The present inventon relates to electric vacuum cleaners capable of suctioning both dry particulate materials and liquids and particularly to means at the exit from the collecting tank of a vacuum cleaner for halting suction at the same level of fill of the tank regardless of whether a mixture of liquid and air or merely liquid is being suctioned.
An electric vacuum cleaner broadly includes suction means, for generating suction force, a suction inlet through which material is to be suctioned and a collecting means or tank disposed between the suction inlet and the suction means. Without limitation to one type of vacuum cleaner, the present invention is shown in a tank or cannister type electric vacuum cleaner, where the collecting means is a large tank or drum, the suction inlet to the tank is through a port in the side of the tank or at the top of the tank and the suction means is supported at the lid of the tank and communicates into the tank for suctioning air out of the tank and thereby for generating suction force at the suction inlet. A hose with an intake nozzle remote from the suction inlet port is received in that port. The suction means is a blower motor, having its inlet communicating into the tank for generating a vacuum in the tank and having its outlet communicating externally of the tank and of the motor. The blower motor may be a bypass type motor, which has a separate cooling air circuit for cooling the motor. The entire cooling air circuit is external of the tank and is not pertinent here.
Filter means are disposed before the exit from the tank to the blower motor to retain collected particulate materials in the tank while permitting exit of air that has been pulled through the tank.
It is desirable to halt intake through the suction inlet when the tank becomes filled. This is a safety measure. When the tank becomes filled with particulate materials, which cannot pass the filter and which thus block the filter, the passage of air to the blower motor will be inhibited and suction will be halted. The invention is not directed to solving a problem experienced with dry material pickup.
Where the vacuum cleaner also is intended for suctioning liquid into the tank, because the liquid can permeate through the filter when the tank is eventually filled with collected liquid up to the filter, the liquid will pass the filter and will be suctioned through the tank outlet and through the section motor, undesirably expelling the collected liquid and possibly damaging the motor. Therefore, means are required to shut off suction by the blower motor when the tank becomes filled with liquid. To this end, it is conventional to provide a filter supporting cage extending down into the tank and surrounding the exit from the tank. A replaceable filter is installed on and supported by the cage.
Inside the filter cage is an element, such as a ball, which normally rests on the bottom of the cage, spaced away from the exit from the tank. The element is adapted to float on liquid, and when liquid fills the tank up to the filter cage and then passes through the filter into the cage, the floatable element or ball is floated up toward the tank exit. As the element approaches the exit, the suction force at the exit eventually draws the element which has floated up to it securely against the exit to thereafter block further air flow through the tank exit.
The filter cage serves as a guide for the floatable element to keep it beneath the air exit and guides it to float up to that exit. The filter cage and the floatable shut-off element in the cage are both shaped and positioned so that the element is spaced far enough away from the tank exit that the element must travel a considerable distance to shut off flow at the tank exit. This assures that the element does not prematurely pop up and close off the exit.
The vacuum cleaner takes in liquid in two different ways, either mixed with air in an air stream or as a stream of liquid not mixed with air. The intake of mixed air and liquid occurs when a surface having a small spill of liquid on it is being suctioned. In this case, the air flow through the tank exit is quite rapid. The intake of liquid alone occurs when liquid is being suctioned from a deep pool or supply, as from a sink, tub or tank, and where the inlet end of the suction hose is entirely submerged, so no air is sucked into the tank along with the liquid. In this case, there is very small air flow through the tank exit.
The different rates at which air exits from the tank will cause the floatable element or ball to seal the tank exit at different levels of fill of the tank. When the liquid in the tank has risen sufficiently to float the floatable element up through the filter cage, while the vacuum cleaner is suctioning mixed air and liquid so that the amount of air flow is higher, the floatable element is lifted off the rising pool of liquid in the filter cage and is sucked against the tank exit by the rapid air flow and pressure differential after the ball has been floated up to a first height. When the vacuum cleaner is suctioning liquid alone while the floatable element is floating up through the filter cage on the rising pool of liquid, because the air flow velocity through the tank exit is greatly reduced and there is little or no pressure differential, the floatable element is not lifted off the pool of liquid and sucked against the tank exit until the pool of liquid has risen to a second height, higher than the aforementioned first height. Thus, where mixed liquid and air is being suctioned, suction is terminated at an earlier time, with the tank less full, than when liquid alone is being suctioned, without air. Clearly, the maximum level of filling of the tank is dependent not merely upon the capacity of the tank, but upon the form in which the liquid is being suctioned into the tank at the time that the floatable element is floating up toward the tank exit on the rising pool of collected liquid. The difference between the first height of fill of the tank and the second height of the fill of the tank is about 2 inches or 5 cm.